import pygame
from pygame.locals import *

pygame.init()
screen = pygame.display.set_mode((600, 600))
is_loop = True
y = 50
clock = pygame.time.Clock()
while is_loop:
    for event in pygame.event.get():
        if event.type == QUIT:
           is_loop=False
    screen.fill((0,0,0))
    pygame.draw.circle(screen, (255, 0,0), (300, y), 20)
    y+=1
    clock.tick(100)
    pygame.display.update()

pygame.quit()